By Dogyun Kim, Daewoung Kim and Hyonhee Shin SEOUL (Reuters) – Plunging prices for Russian crab have South Koreans flocking to seafood markets and restaurants but some consumers are questioning whether to boycott the imports on concerns the purchases indirectly support Russia’s invasion of Ukraine. The dinner-plate sized king crabs from Russia, along with slightly smaller snow crabs and lobsters, were once a pricey delicacy in South Korea, though they have become more popular at supermarkets and online retailers in recent years. But prices have nearly halved since late February as the United S…